The present invention relates to the manufacturing of components made from composite materials, and more particularly, to an in-jig assembly bond fixture for manufacturing composite components having multiple subcomponents, such as a composite gas turbine engine component or the like.
Composite materials are gaining wider application and use as a material for aerospace applications and the like, and in particular the manufacturing of gas turbine engine components, such as those used in high performance engines for aircraft propulsion, because of the light weight and high strength of these composite components. Such aircraft engine components may include an engine front frame, a fan stator assembly or an airfoil type engine assembly. An example of a composite gas turbine engine component is the front frame engine assembly 10 shown in FIG. 1. Referring also to FIGS. 2 and 3, the front frame assembly 10 includes an annular outer forward case 12, an inner hub 14 and a plurality of intermediate radially extending strut members 16 which are attached between the annular case 12 and the inner hub 14. As best shown in FIG. 3, strut 16 includes an outer end 18 having outer strut feet 20, which extend substantially perpendicular to the longitudinal extent of strut 16, and radially extending flanges 22 extending substantially perpendicular from strut feet 20. Both strut feet 20 and flanges 22 are attached or bonded to case 12 during manufacturing. Strut 16 further includes an inner end 24 having inner strut feet 26 extending substantially perpendicular to the longitudinal extent of strut 16 and radial flange 28 extending substantially perpendicular from inner strut feet 26. Inner strut feet 26 and flange 28 are attached or bonded to inner hub 14 during manufacturing. An aft annular casing 30 is bonded to forward casing 12 as shown in FIG. 1 after assembly of the forward case.
The frame, therefore, represents a very complex assembly of sub-components which must be bonded together using high temperature adhesives. The assembly of these different components into the frame 10 represents a formidable manufacturing challenge. The bonded joints must be maintained at a specific bond line thickness to ensure strength while the adjacent constituents are held accurately in place during the curing cycle. Because of tight tolerances, positioning of the components is very critical and must be accurately controlled to ensure proper airfoil orientation and the proper air flow path through the engine during operation of the assembled engine.
A prior art arrangement for retaining the different components in proper alignment during a curing cycle in an oven utilized C-clamps, jack screws and paste adhesive. The different constituents were prepared with the paste adhesive and oriented relative to one another and secured in position by tightening the hand jack screws, C-clamps or toggle clamps. This arrangement and method provided no control or reliability as to the integrity of the finished assembly. This oven fixture provided no internal heating or uniform pressure on the different bond joints during the curing cycle to ensure a specific bond line thickness and that the different constituents remained in their proper orientation relative to one another. Additionally, this fixture had no internal monitoring to verify or control that the proper amounts of heat and pressure were being applied to each respective bond joint. The pressure applied was merely as a result of the clamping mechanics of the jack screws, C-clamps or toggle clamps and maintenance of a constant uniform pressure was suspect during a curing cycle because of the susceptibility of these different clamps to thermal growth and distortion caused by the heat of the curing oven. The temperature of the oven could be controlled by a thermocouple; however, there was no actual monitoring and control of the bond temperatures at the individual joints of the assembly or monitoring and control of the bonding at critical bonding surfaces.
Thus, there was a need for a new in-jig assembly bond fixture which was a self-contained, stand-alone, integrally heated and pressurized unit including a computer controlled/integrated system for monitoring and controlling the bonding operation at the different bond joints and at critical bonding surfaces.